Brown tells MSNBC Hardball host Chris Matthews that he'll step up his campaign for California governor before Labor Day. He says he won't let former eBay chief executive Meg Whitman buy the race with her own fortune.

Brown on Friday also defended his decision not to immediately respond to any of Whitman's recent television commercials with his own paid advertising.

Since winning the Republican primary in June, Whitman has been airing at least three TV ads statewide. A union-backed group is running its own ads supporting Brown.

A Field Poll released earlier this week showed the two are virtually tied.